Density isn't the sole consideration. Wood is chosen for tool handles based upon one's personal preference for trading off strength for toughness and elasticity. Oak is dense and hard, yet not very elastic; repeated impacts are going to stress the wood until it gives way spectacularly, usually with a bunch of stabby fragments. Ash or Hickory are also dense and hard, but are capable of soaking up the repeated impacts of tool use with the added benefit of often giving warning signs that they are about to break. On the other end of the spectrum is White Waxwood, which is not terribly dense or hard in comparison, but is extremely resilient to impact--though it really likes to rot.
The length of the tool matters a lot, as does the weight of the tool head, and the intended use. A pike needs to be made of stiff wood or it's going to droop and wobble at the business end. There will be less torque on it from side impact on that long lever arm, so toughness and flexibility are less useful when the primary load will be coming along the longitudinal axis. A big scythe head on a pole will be introducing large amounts of torque to that pole, so the wood will require toughness more than density.
There are a few ways to cheat, like using coppiced wood or shade-grown hardwoods that have very thin growth rings, but the basic properties of the wood only move so far. There's a reason why Ash and Hickory have been popular woods for tools for as long as we have been making them. The Exotics can be a lot of fun though, and my favorite mallet is 3lbs of Lignum Vitae on a Purpleheart haft, so it would be interesting to try Quebracho if I could ever find any. Whenever I get too picky about wood, I remind myself that Bamboo spears have probably changed more regimes through history than any other weapon.
